In a semiconductor thin film forming step, an etching step, a resist film baking step, or other step to be followed in a semiconductor manufacturing process, a wafer heating apparatus is used to heat a semiconductor wafer (hereafter abbreviated as “wafer”). The wafer heating apparatus is put to use when incorporated in a semiconductor manufacturing apparatus. Examples of such a wafer heating apparatus include a heater disclosed in Japanese Unexamined Patent Publication JP-A 2001-244057 (hereafter referred to as “Patent Literature 1”). The heater disclosed in Patent Literature 1 comprises a heat-equalizing plate formed of ceramics, a SiO2 film formed on the surface of the heat-equalizing plate, a glass-made insulating layer formed on the surface of the SiO2 film, and a heating resistor disposed on the surface of the insulating layer. The heating resistor is electrically connected to a rod-like electrically conductive terminal (connection terminal) via a feeder portion (conductive layer). The connection between the connection terminal and the conductive layer is maintained under the condition where the connection terminal is pressed against the conductive layer. The heater is used to heat an object to be heated, such as a wafer, on the upper surface of the heat-equalizing plate.
In the heater disclosed in Patent Literature 1, however, since the connection between the connection terminal and the conductive layer is established by pressing the connection terminal against the conductive layer, it is difficult to achieve improvement in the long-term reliability of electrical connection between the connection terminal and the conductive layer. More specifically, there may be cases where a pressing force exerted between the connection terminal and the conductive layer varies under heat cycles. At this time, too great a pressing force may cause damage to the connection terminal or the conductive layer. On the other hand, too small a pressing force may cause a failure in maintaining the electrical connection between the connection terminal and the conductive layer.
The invention has been devised in view of the problem as discussed above, and accordingly an object thereof is to provide a heater capable of achieving improvement in long-term reliability of electrical connection between a connection terminal and a conductive layer.